Adaptive in-loop filtering for video coding

1. A video coding system comprising: a memory to store first and second pictures of first and second groups of pictures, respectively, of video for coding; and a processor coupled to the memory, the processor to: determine, for the first and second pictures, first and second picture level maximum coding bit limits and picture level quantization parameters, respectively; set a first picture level in-loop filter indicator for the first picture to off, to indicate one of constrained directional enhancement filtering or loop restoration filtering is to be bypassed for the first picture, responsive to the first picture level maximum coding bit limit comparing unfavorably to a first threshold and the first picture level quantization parameter comparing favorably to a second threshold; set a second picture level in-loop filter indicator for the second picture based at least in part on a comparison of the second picture level maximum coding bit limit to the first threshold and the second picture level quantization parameter to the second threshold; and code the first and second pictures based at least in part on the first and second picture level in-loop filter indicators to generate a bitstream.

2. The video coding system of claim 1 , wherein the bitstream comprises an Alliance for Open Media compliant bitstream.

3. The video coding system of claim 1 , wherein, responsive to the second picture level maximum coding bit limit comparing favorably to the first threshold or the second picture level quantization parameter comparing unfavorably to the second threshold, the processor is further to: determine whether the second picture is a scene change picture; and set the second picture level in-loop filter indicator to on responsive to the second picture being a scene change picture.

4. The video coding system of claim 1 , wherein, responsive to the second picture level maximum coding bit limit comparing favorably to the first threshold or the second picture level quantization parameter comparing unfavorably to the second threshold, the processor is further to: set the second picture level in-loop filter indicator for the second picture based on a coding structure associated with coding the second group of pictures.

5. The video coding system of claim 4 , wherein the coding structure comprises a hierarchical B structure, the second picture is a non-reference B-picture, and the processor to set the second picture level in-loop filter indicator for the second picture comprises the processor to set the second picture level in-loop filter indicator to off responsive to the second picture being a non-reference B-picture.

6. The video coding system of claim 4 , wherein the coding structure comprises a hierarchical B structure, the second picture is a non-reference B-picture or a reference B-picture that can only be referenced by non-reference B-pictures, and the processor to set the second picture level in-loop filter indicator for the second picture comprises the processor to set the second picture level in-loop filter indicator to off responsive to the second picture being a non-reference B-picture or a reference B-picture that can only be referenced by non-reference B-pictures.

7. The video coding system of claim 4 , wherein the coding structure comprises a low delay coding structure having a constant maximum coding bit limit for pictures other than a first temporal picture of the second group of pictures and the processor to set the second picture level in-loop filter indicator for the second picture comprises the processor to set picture level in-loop filter indicators to off for the second group of pictures at a fixed picture interval.

8. The video coding system of claim 4 , wherein the coding structure comprises an adaptive quantization parameter low delay coding structure and the processor to set the second picture level in-loop filter indicator for the second picture comprises the processor to set the second picture level in-loop filter indicator to off responsive to a high quantization parameter being associated with the second picture and to set the second picture level in-loop filter indicator to on responsive to a low quantization parameter being associated with the second picture.

9. The video coding system of claim 4 , wherein the coding structure comprises at least one I-picture, the second picture is an I-picture, and the processor to set the second picture level in-loop filter indicator comprises the processor to set the second picture level in-loop filter indicator to on responsive to the individual picture being an I-picture.

10. The video coding system of claim 1 , wherein, responsive to the second picture level in-loop filter indicator being set to on based on the comparison of the second picture level maximum coding bit limit to the first threshold and the second picture level quantization parameter to the second threshold, the processor is further to: determine the second picture matches a reference picture associated with the second picture; and set, prior to coding the second picture, the second picture level in-loop filter indicator for the second picture to off responsive to the individual picture matching the reference picture.

11. The video coding system of claim 1 , wherein, responsive to the second picture level in-loop filter indicator being set to on based on the comparison of the second picture level maximum coding bit limit to the first threshold and the second picture level quantization parameter to the second threshold, the processor is further to: determine, for a coding unit of the second picture, at least one of a motion vector associated with the coding unit is a zero motion vector or a prediction residue associated with the coding compares favorably to a third threshold; set a coding unit level in-loop filter indicator for the coding unit to off responsive to the coding unit having a zero vector motion vector or a prediction residue that compares unfavorably to the third threshold; and skip in-loop filtering for the coding unit responsive to the coding unit level in-loop filter indicator being off for the coding unit.

12. The video coding system of claim 1 , wherein, responsive to the second picture level in-loop filter indicator being set to on based on the comparison of the second picture level maximum coding bit limit to the first threshold and the second picture level quantization parameter to the second threshold, the processor is further to: determine, for a coding unit of the second picture, a motion vector associated with the coding unit is a zero motion vector and a reference coding unit corresponding to the coding unit has a quantization parameter that compares favorably to a third threshold; set a coding unit level in-loop filter indicator for the coding unit to skip responsive to the coding unit having a zero vector motion vector and the coding unit having a quantization parameter that compares favorably to the third threshold; skip in-loop filter selection for the coding unit responsive to the coding unit level in-loop filter indicator being skip for the coding unit; and perform in-loop filtering for the coding unit using in-loop filter parameters from a reference coding unit.

13. A computer-implemented method for video coding comprising: determining, for first and second pictures of first and second groups of pictures, respectively, first and second picture level maximum coding bit limits and picture level quantization parameters, respectively; setting a first picture level in-loop filter indicator for the first picture to off, to indicate one of constrained directional enhancement filtering or loop restoration filtering is to be bypassed for the first picture, responsive to the first picture level maximum coding bit limit comparing unfavorably to a first threshold and the first picture level quantization parameter comparing favorably to a second threshold; setting a second picture level in-loop filter indicator for the second picture based at least in part on a comparison of the second picture level maximum coding bit limit to the first threshold and the second picture level quantization parameter to the second threshold; and coding the first and second pictures based at least in part on the first and second picture level in-loop filter indicators to generate a bitstream.

14. The method of claim 13 , wherein, responsive to the second picture level maximum coding bit limit comparing favorably to the first threshold or the second picture level quantization parameter comparing unfavorably to the second threshold, the method further comprises: setting the second picture level in-loop filter indicator for the second picture based on a coding structure associated with coding the second group of pictures, wherein the coding structure comprises a hierarchical B structure, the second picture is a non-reference B-picture, and setting the second picture level in-loop filter indicator for the second picture comprises setting the second picture level in-loop filter indicator to off responsive to the second picture being a non-reference B-picture.

15. The method of claim 13 , wherein, responsive to the second picture level maximum coding bit limit comparing favorably to the first threshold or the second picture level quantization parameter comparing unfavorably to the second threshold, the method further comprises: setting the second picture level in-loop filter indicator for the second picture based on a coding structure associated with coding the second group of pictures, wherein the coding structure comprises a low delay coding structure having a constant maximum coding bit limit for pictures other than a first temporal picture of the second group of pictures and setting the second picture level in-loop filter indicator for the second picture comprises setting in-loop filter indicators to off for the second group of pictures at a fixed picture interval.

16. The method of claim 13 , wherein, responsive to the second picture level maximum coding bit limit comparing favorably to the first threshold or the second picture level quantization parameter comparing unfavorably to the second threshold, the method further comprises: setting the second picture level in-loop filter indicator for the second picture based on a coding structure associated with coding the second group of pictures, wherein the coding structure comprises an adaptive quantization parameter low delay coding structure and setting the second picture level in-loop filter indicator for the second picture comprises setting the second picture level in-loop filter indicator to off when a high quantization parameter is associated with the second picture and setting the second picture level in-loop filter indicator to on when a low quantization parameter is associated with the second picture.

17. The method of claim 13 , wherein, responsive to the second picture level in-loop filter indicator being set to on for the second picture, the method further comprises: determining, for a coding unit of the second picture, at least one of a motion vector associated with the coding unit is a zero motion vector or a prediction residue associated with the coding compares favorably to a third threshold; setting a coding unit level in-loop filter indicator for the coding unit to off responsive to the coding unit having a zero vector motion vector or a prediction residue that compares favorably to the third threshold; and skipping in-loop filtering for the coding unit responsive to the coding unit level in-loop filter indicator being off for the coding unit.

18. At least one non-transitory machine readable medium comprising a plurality of instructions that, in response to being executed on a computing device, cause the computing device to perform video coding by: determining, for first and second pictures of first and second groups of pictures, respectively, first and second picture level maximum coding bit limits and picture level quantization parameters, respectively; setting a first picture level in-loop filter indicator for the first picture to off, to indicate one of constrained directional enhancement filtering or loop restoration filtering is to be bypassed for the first picture, responsive to the first picture level maximum coding bit limit comparing unfavorably to a first threshold and the first picture level quantization parameter comparing favorably to a second threshold; setting a second picture level in-loop filter indicator for the second picture based at least in part on a comparison of the second picture level maximum coding bit limit to the first threshold and the second picture level quantization parameter to the second threshold; and coding the first and second pictures based at least in part on the first and second picture level in-loop filter indicators to generate a bitstream.

19. The non-transitory machine readable medium of claim 18 further comprising instructions that, in response to being executed on the computing device, cause the computing device to perform video coding by: setting, responsive to the second picture level maximum coding bit limit comparing favorably to the first threshold or the second picture level quantization parameter comparing unfavorably to the second threshold, the second picture level in-loop filter indicator for the second picture based on a coding structure associated with coding the second group of pictures, wherein the coding structure comprises a hierarchical B structure, the second picture is a non-reference B-picture, and setting the second picture level in-loop filter indicator for the second picture comprises setting the second picture level in-loop filter indicator to off responsive to the second picture being a non-reference B-picture.

20. The non-transitory machine readable medium of claim 18 further comprising instructions that, in response to being executed on the computing device, cause the computing device to perform video coding by: setting, responsive to the second picture level maximum coding bit limit comparing favorably to the first threshold or the second picture level quantization parameter comparing unfavorably to the second threshold, the second picture level in-loop filter indicator for the second picture based on a coding structure associated with coding the second group of pictures, wherein the coding structure comprises a low delay coding structure having a constant maximum coding bit limit for pictures other than a first temporal picture of the group of pictures and setting the in-loop filter indicator for the second picture comprises setting in-loop filter indicators to off for the group of pictures at a fixed picture interval.

21. The non-transitory machine readable medium of claim 18 further comprising instructions that, in response to being executed on the computing device, cause the computing device to perform video coding by: setting, responsive to the second picture level maximum coding bit limit comparing favorably to the first threshold or the second picture level quantization parameter comparing unfavorably to the second threshold, the second picture level in-loop filter indicator for the second picture based on a coding structure associated with coding the second group of pictures, wherein the coding structure comprises an adaptive quantization parameter low delay coding structure and setting the second picture level in-loop filter indicator for the second picture comprises setting the second picture level in-loop filter indicator to off when a high quantization parameter is associated with the second picture and setting the second picture level in-loop filter indicator to on when a low quantization parameter is associated with the second picture.

22. The non-transitory machine readable medium of claim 18 further comprising instructions that, in response to being executed on the computing device, cause the computing device to perform video coding by: determining, responsive to the second in loop filter indicator being set to on and for a coding unit of the second picture, at least one of a motion vector associated with the coding unit is a zero motion vector or a prediction residue associated with the coding unit compares favorably to a third threshold; setting a coding unit level in-loop filter indicator for the coding unit to off responsive to the coding unit having a zero vector motion vector or a prediction residue that compares unfavorably to the third threshold; and skipping in-loop filtering for the coding unit responsive to the coding unit level in-loop filter indicator being off for the coding unit.